Comparison Between I2C Expansion Board and I2C Transfer Board
Model Name I2C Expansion Board I2C Transfer Board
Port Quantity 7P 4P
Definition of Ports 1 Input Port and 6 I2C Ports 1 Input Port, 2 I2C Ports and 1 GPS Serial Port
Functions Extention of I2C Port Only Extention of I2C Port and GPS Serial Port
Obstacle Avoidance of Six Synchronous Direction (Overall) Obstacle Avoidance of Arbitraty Two Synchronous Directions 
FC Compatibility Compatible with RadioLink Mini Pix/TURBO PiX/PIXHAWK and Open Sourced PIXHAWK
Obstacle Avoidance Ultrasonic Sensor Compatibility Compatible with RadioLink Ultrasonic Sensor of Obstacle Avoidance SU04/SUI04
Remark When GPS and ultrasonic sensors need to be connected at the same time, a transfer board is essential to connect with the GPS/I2C port of flight controller first, then expansion board to the transfer board. Two I2C ports can be used to connect with corresponding I2C modules such as one ultrasonic sensor SU04 to achieve altitude holding and an LED module.
Accessory, Purchased Individually TURBO PiX Standard Pack